1. Field of the Invention
The present invention relates to a method of conveying blanked sheet pieces out of a punch press provided with a blanking die assembly having upstream cutter units and downstream cutter units for cutting across an elongated sheet material fed into the press along two lines spaced apart in the direction of feed in each striking stroke of the press, thereby blanking out simultaneously two sheet pieces from the elongated sheet material in each striking stroke.
The present invention relates also to a blanking die assembly of such type.
2. Description of Prior Art
In a punch press associated with a conventional blanking die assembly of this type, one of the two blanked out sheet pieces or workpieces located downstream with respect to the other is conveyed downstream out of the press to a sheet stacker, while the other upstream located sheet piece is conveyed transversely out of the press to another sheet stacker. This is because there has been no suitable method of transporting the upstream located workpiece in a downstream direction. Stated otherwise, the prior art apparatus associated with a blanking die assembly of this type has no means for forcibly transferring workpieces of predetermined size in a short period of time. The foregoing conventional transporting method has suffered from two problems. The first problem is that a sheet stacker has to be installed outside the direction of feed in addition to the one located downstream with respect to the direction of the feed. The second problem is that since the apparatus is arranged such that the upstream blanked out workpiece falls freely onto a conveyor which transversely transports it out of the press, it is impossible to provide means at the blanking-out location for supporting the sheet material from below, as with skid bars. Therefore, a magnetic roll or the like which will attract the sheet material must be attached to the upper die base to support the leading end portion of the sheet material when the sheet material is fed into the press. This arrangement results in unstable feeding and is an obstacle to speeding up the operation.